When an electrical power is supplied to an information processing apparatus such as a server apparatus, a primary power supply (AC power supply) supplied from a commercial power supply is converted into a secondary power supply (low voltage DC power supply) by a power source unit provided in the apparatus and the power is supplied to respective places on a board such as a motherboard provided in the apparatus. The power is supplied to each component after a voltage value of the power to be supplied to respective places on the board is further converted into a voltage value corresponding to each component by a DC/DC converter. When electrical power is supplied to a processor such as a CPU (Central Processing Unit), the power is supplied to the processor after the voltage value of the power to be supplied to respective places on the board is further converted into a voltage value corresponding to the processor by a DC/DC converter.
For example, as illustrated in FIG. 9, a CPU 111, a DIMM (Dual Inline Memory Module) 112, a DC/DC converter 113, and a high-speed signal transmission component 114 are mounted on the same plane of the board 101. As illustrated in FIG. 10, power is supplied from the DC/DC converter 113 to the CPU 111 through a plurality of power feeding paths 121 formed in the board 101. Further, as illustrated in FIG. 10, a plurality of signal transmission paths 122 is formed in the board 101. FIG. 9 is a plan view of the board 101 and FIG. 10 is a partial cross sectional view of the board 101.
The DC/DC converter 113 outputs a voltage which compensates a voltage drop occurring on the way of a power feeding path 121 in order to supply the power to the CPU 111 at a predetermined voltage. Accordingly, the DC/DC converter 113 is provided in the vicinity of the CPU 111 so as to reduce the voltage drop. The signal is transmitted at a higher speed in the server apparatus as a transmission distance between the CPU 111 and a memory such as the DIMM 112 becomes smaller, and thus the performance of the server apparatus is enhanced. For example, as illustrated in FIG. 9, the DIMM 112 or the high-speed signal transmission component 114 is arranged in the vicinity of the CPU 111 so as to make the transmission distance between the CPU 111 and the DIMM 112 shorter and make the transmission distance between the CPU 111 and the high-speed signal transmission component 114 shorter as well.
In recent years, since a demand for a high-performance server apparatus is increasing, an improvement in the performance of a processor, a speeding up of signal transmission, and an increase of a memory capacity are required. The performance of processor is improved by increasing the frequency of the processor. For example, since the power consumption of the CPU 111 increases when the frequency of the CPU 111 is increased, large current is supplied to the CPU 111 by increasing the number of the DC/DC converters 113. When there is no empty area capable of accommodating the DC/DC converter 113 in the board 101, an outer appearance of the board 101 is made larger so as to increase the number of the DC/DC converters 113 as illustrated in, for example, FIG. 11. When the outer appearance of the board 101 becomes larger and a manufacturing size of the board 101 is out of a standard size, it becomes difficult to manufacture the board 101 or the manufacturing cost of the board 101 is increased.
When the number of the DC/DC converters 113 is increased, a power feeding path 121 extending from the DC/DC converter 113 to the CPU 111 is added. As illustrated in FIG. 10, since a plurality of signal transmission paths 122 is formed in the board 101, the power feeding paths 121 to be added are formed in the board 101 by avoiding the signal transmission path 122. In this case, the number of inner layers of the board 101 is increased so as to secure the power feeding path 121 to be added in the board 101. In a case where the number of inner layers of the board 101 is increased and the manufacturing thickness of the board 101 is out of a standard thickness, it becomes difficult to manufacture the board 101 or the manufacturing cost of the board 101 is increased.
As illustrated in FIG. 12A and FIG. 12B, when the power feeding path 121 extending from the DC/DC converter 113 to CPU 111 is added, the power feeding path 121 is designed to avoid the signal transmission path 122 between the CPU 111 and the DIMM 112. FIG. 12A is a plan view of the board 101 before the power feeding path 121 is added. FIG. 12B is a plan view of the board 101 after the power feeding path 121 is added. In this case, since the power feeding path 121 to be added is formed in the board 101 while avoiding the signal transmission path 122, the power feeding path 121 becomes longer and thinner and thus the influence of voltage drop is increased. Further, when the power feeding path 121 becomes closer to the signal transmission path 122, power supply noise interferes with the signal transmission path 122 such that the transmission performance is decreased.
The followings are reference documents.
[Document 1] International Publication Pamphlet No. WO 2004/004000,
[Document 2] International Publication Pamphlet No. WO 2007/129526, and
[Document 3] Japanese National Publication of International Patent Application No. 2003-518759.